(function(doc, win){
  var docEl = doc.documentElement,
      resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
      recalc = function(){
          var clientWidth = docEl.clientWidth;
          if(!clientWidth) return;
          if(clientWidth>750){
              clientWidth=750;
          }
          docEl.style.fontSize = 20 * (clientWidth / 375) + 'px';
      };

  if(!doc.addEventListener) return;
  win.addEventListener(resizeEvt, recalc, false);
  doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);
